1. Field of the Invention
The invention relates generally to an in-line material handling system and, more particularly, to an in-line material handling system wherein workpieces are transported through the system in pallet baskets.
2. Background of the Invention
When cutting a workpiece, such as a metal plate, with either a plasma arc or an oxy fuel torch, it is known to use a cutting station having a water table with a water bath having an adjustable level. The plate to be cut is immersed in the water bath or positioned above the surface of the water bath so that during the cutting operation, the cut pieces and skeletal remains of the plate are supported above the water bath while the swarf and dross produced during the cutting operation fall into, and are quenched by, the water in the water bath. For such cutting operations, it is also advantageous to use an in-line material handling system to transport the metal plate to and from the cutting station in order to minimize the time required to transport the plate between the stations in the system.
An in-line material handling system having a water table is disclosed in U.S. Pat. No. 4,220,318, the disclosures of which are incorporated herein by reference. In that patent, the metal plate or workpiece to be cut is loaded directly onto the rollers of a first conveyor and is transported onto a second conveyor. The second conveyor includes a number of continuous chains formed by links which are driven by an electric gear motor over sprockets mounted at opposite ends of the conveyor. A series of burning bars are carried on guard elements mounted directly on the links of the chains and the metal plate rests directly on the upper edges of the burning bars on the second conveyor. The guard elements form a channel which is designed to collect slag and dross produced during the cutting operation. When the second conveyor advances to the downstream end of the system, the slag collected in the channels of the guard elements is dumped into a waste container. The second conveyor serves as both a supporting conveyor for the plate during the cutting operation and as an off-loading conveyor.
A cutting station is positioned along the second conveyor and a conventional "bridge" type cutting machine extends over the sides of the second conveyor at the cutting station. A water table having a water tank which provides a water bath is located below the cutting machine. The water table includes sealing elements in the form of doors which, in a retracted position, allow the second conveyor to move freely through the water table beneath the cutting machine. When the plate to be cut is in position under the cutting machine, sealing elements are engaged to seal against the ends of the water tank of the water table so that the water in the water tank can be raised to a predetermined level appropriate to the metal being cut.
After a first metal plate has been cut at the cutting station, the water level in the water tank is lowered to a predetermined low position and the sealing elements are retracted. The second conveyor is then used to transport the cut pieces and metal skeleton produced from the first metal plate, which are resting directly on top of the burning bars of the second conveyor, to an off-loading station while at the same time indexing a new metal plate into position on the cutting station to be cut. When the new metal plate is in position at the cutting station, the second conveyor is stopped, the sealing elements are engaged, the water level in the water tank is adjusted and cutting is begun on the new metal plate. While the new metal plate is cut, the cut pieces and the metal skeleton from the first metal plate are individually removed from the top of the second conveyor at an off-loading station.
The cut pieces at the off-loading station generally consist of a number of individual metal pieces having a variety of shapes and sizes. Removing these cut pieces is a tedious and time consuming step which usually requires much more time than the time required to cut a plate at the cutting station. Therefore, it is not uncommon that pieces from a previously cut plate are still being off loaded from the second conveyor at the off-loading station when the cutting of the plate at the cutting station is completed. Thus, the second conveyor cannot be indexed forward to transport the cut plate out of the cutting station and transport another plate into the cutting station. This results in the loss of valuable cutting time while the cutting station is idle due to the time required to complete the off loading of the cut pieces and metal skeleton from the previously cut plate at the off-loading station. This loss of cutting time in the prior art cutting systems is undesirable lost production. Further lost production occurs due to the time required to separate poorly cut pieces, to repair and replace burning bars attached to the second conveyor and for multiple handling of cut parts and scrap. In the prior art handling systems, the off loading of the cut metal pieces from the second conveyor is the time controlling function in the operation of the overall system.
In addition, current plasma cutting technology utilizes oxygen which makes it attractive to cut a metal plate in the atmosphere in some situations. However, cutting plates in the atmosphere in the prior art cutting system produced large volumes of smoke and fumes. The smoke and fumes irritates workers near the cutting station and also creates a respiratory hazard away from the cutting station. Further, the Environmental Protection Agency requirements for the treatment of processed water are becoming more and more stringent and the cost of treating the water discharged from the water tank is expensive. Hence, a need for fume collection and air handling/filtration in cutting systems has developed as well as a need to effectively treat the water used in the water bath to remove the contaminants produced during the cutting operation.
Therefore, it is an object of the present invention to provide a device for quickly and efficiently off loading both cut pieces and skeletal remains from an in-line material handling system to increase the available cutting time of the system. It is a further object of the present invention to provide a pallet basket which can be used to quickly on load a workpiece onto the in-line material handling system and carry the workpiece and/or cut pieces of the workpiece through the entire in-line handling system. It is also an object of the invention to provide an improved in-line material handling system in which reusable pallet baskets are used to carry the workpiece and/or cut parts through the handling system. It is a further object of the invention to provide an in-line handling system in which the pallet baskets carrying the workpieces are moved through the handling system in carts. It is an additional object of the invention to provide a modified processing station for an in-line handling system which assists in the removal of smoke and fumes generated during atmospheric cutting of a workpiece at the processing station.